Heater ignition system



Sept. 18, 1951 G. JACOBS HEATER IGNITION SYSTEM Filed Nov. 18, 1948Patented Sept. 18, 1951 UNITED STATES PATENT OFFICE HEATER IGNITIONSYSTEM Application November 18, 1948, Serial No. 60,747

2 Claims. 1

The present invention relates to heating systems and more particularlyto a spark ignition system intended to be used as a part of aircraftcombustion type heaters. An aircraft heater of the type illustrated anddescribed in the copending application of Seymour E. Heymann, Serial No.610,978, now Patent No. 2,454,512, burns liquid fuel, usually the samefuel supplied for the aircraft engine and has an extremely high outputconsidering its weight and size. One of the important accessories usedwith such a heater is the system for igniting the fuel. One systemcommonly used for this purpose includes a spark plug which is suppliedwith electric energy at high voltage so as to produce a spark ofsufficient intensity to ignite the fuel and air mixture within theheater.

The present invention is concerned with the provision of such a sparkignition assembly and has as one of its objectives the provision of animproved spark ignition system which is extremely reliable.

Another object is to provide a novel spark ignition system which can beput into operation from a remote point and which can otherwise becontrolled remotely.

Yet another object is to provide an improved spark ignition system whichdoes not interfere with radio and radar equipment with which theairplane usually will be provided.

Still another object is to provide a novel heater ignition system inwhich the components of the system which are most likely to causeservice difliculty may be changed at will during flight even though theheater is located in an inaccessible position.

Other objects and advantages will become apparent from the followingdescription of a preferred embodiment of my invention which isillustrated in the accompanying drawing.

The single figure of the drawing is a diagrammatic representation of anelectrical circuit which embodies the present invention.

The ignition system which comprises the present invention consistsgenerall of a spark plug I located within the combustion heater andnormally forming a part thereof, this spark plug being connected by ashielded cable to a quick disconnect I 2, the other half of which ismounted upon a box, not shown, which contains the major portion of theignition system. High voltage electric current is supplied to thedisconnect l2 and therefore to the spark plug III by the secondary ll ofa step-up transformer [6, the primary I8 of which is supplied withpulsating di rect current from a battery 20 by way of vibrator typecircuit interrupters 22 and 24, the battery being connected to theignition box by way of a quick disconnect 26.

In such an ignition system the weak link, in other words, the elementmost likely to get out of order, is the vibrator 22 or 24. These deviceswhich are commonly available consist in general of a tuned reed whichvibrates in the field of an electromagnet and which rapidly makes andbreaks an output circuit. Although these vibrators, so-called, arecommonly available well engineered devices and well suited in general totheir purpose, the constant sparking at the contacts together with therather large electrical load imposed thereon by the transformer primaryI 8 is likely to cause the vibrators to fail while in use. Such failurein an aircraft heater installation may have rather seriousconsequencies, particularly if the heater is used for anti-icingpurposes. That is, in some applications high output heaters of the typementioned are used for raising the temperature of the wings and tailsurfaces of aircraft so as to prevent the formation of ice thereon. Anyfailure of the heating system thereof may result in the rapidaccumulation of ice upon the aircraft.

It has been found in use that the basic heater,

the spark plug used therewith, the transformer and the other elements ofthe system are quite dependable and that, as mentioned previously, theprincipal service difliculty will be experienced with the vibrator. Inorder to contribute to the safety of this heater, therefore, I haveprovided two vibrators, indicated by the numerals 22 and 24, and have soarranged the circuit that either of these vibrators may be used at thewill of the operator for operating the ignition system. Further, I havearranged for these vibrators to be located within the box usuallyattached to the heater which contains all of the ignition equipment so ato provide for better radio shielding and have arranged the circuit suchthat either of the vibrators may be used at will and such that anoperator can switch from one vibrator to the other by merely actuating amomentary contact push button conveniently disposed at a remotelocation.

Specifically, the circuit comprises the aircraft battery 28, one side ofwhich is grounded while the other side is connected by a lead 28 to thequick disconnect 25, half of which is secured. to the metal boxcontaining the ignition equipment. From the disconnect 25 a lead 35passes to a choke capacitor filter system 32 and thence by way of aconductor 25 to one side of each of the primary [8 and secondary [4 ofthe ignition transformer l6;

As previously mentioned, the other side of the transformer secondary i4is connected to the disconnect l2 and thence to the spark plug [9. Theother side of the transformer primary I8 is connected by a lead 34 to aterminal 35 of the vibrator 22 which in turn is connected by a branch 38to the similar terminal 40 of the other vibrator 24. The vibrator 24also has a second terminal 42 connected by a lead 44 to the similarterminal 46 of the other vibrator 22 and to ground. A 9.25 m. f. d.capacitor 48 is also connected between the ground point of the lead 44and the lead'34 leading to the ignition transformer primary for thepurpose of suppressing arcing at the vibrator contacts.

A stepping relay 59 which may be of any wellknown construction is of thesingle pole double throw type and comprises a swinging contact member 52which in one position is associated with a stationary contact 54 whilein the other position the movable member 52 is connected to anotherstationary contact 55. The movable member 52 is operated by anelectromagnetic coil 58 and the mechanism is so arranged that when thecoil 58 is momentarily energized the movable member 58 will be shiftedfrom one position to the other. Whenever the coil 58 is againmomentarily energized the movable member 52 will be shifted back to itsoriginal position and so on. One side of the coil 58 is grounded whilethe other side thereof is connected by a lead 59' through a normallyopen push button 52 to the previously mentioned lead 25.

The push button 52 is mounted upon the metal ignition box and thecircuit is such that whenever the push button 62 is depressedrnomentarily the coil 58 will be momentarily energized, thereby shiftingthe position of the movable contact 52 of the stepping relay. Theungrounded side 28 of the battery 29 is also connected through a lead 54and push button 66 to one-half of a quick disconnect 68. The other halfof this disconnect is mounted upon the ignition box and internally ofthe box is connected to a lead 70 which passes through a choke capacitorfilter network 12 and thence to the lead 60 at a point between the pushbutton 92 and the coil 58. The push button 55 is remotely located withinreach of one of the crew men of the aircraft and serves when actuated toenergize the coil 58 momentarily so as to shift the position of thestepping relay 59 in the same manner that the position of the relay isshifted by the push button 52.

The stationary contact 56 of the stepping relay switch is connected byconductor '34 to a terminal of the vibrator 22 while a similar terminal78 of the vibrator 24 is connected by a lead 59 to the other stationarycontact 54 of the step-ping relay switch. The swinging element 52 ofthis switch is connected by a lead 82 to the lead by way of a resistor84 which in the present instance has a resistance of approximately ohms.

The internal circuit of the vibrator 22 comprises the vibrating reed 85previously referred to which is connected to the terminal 46. This reedis also electrically connected to one end of a magnetic coil 83, theother end of which is connected to the terminal 75. The vibrator has twostationary contacts therein adapted to be engaged by the vibrating reed83 alternately when the reed is in the alternate extreme positions.

4 One of the stationary contacts is indicated by the numeral 99 and isconnected to the terminal 36. The other stationary contact, indicated bythe numeral 92 is, as is one end of the coil 88, connected to theterminal 16.

The elements of the vibrator 24 duplicate those of the vibrator 22 sothat the vibrating reed 94 of the vibrator 24 is the counterpart of thereed 86 previously mentioned. Similarly, contacts 95 and 98 arecounterparts of the contacts 99 and 92 and the coil Hill is thecounterpart of coil 88.

The circuit operates in the following manner. Assuming that thedisconnects 25, 28 and i2 are properly joined and that the steppingrelay is in the position shown with movable contact '52 againststationary contact 54, it will be seen that electric power is suppliedfrom the battery 29 through the disconnect 28 and filter system 32 tothe lead 25 and thence to one side of the transformer primary [8. Thislead is also connected to the secondary Hi. The lead 34 is thereforeenergized through the transformer primary and therefore raises thepotential of the vibrator contacts 99 and 55 to that of the battery. Nocurrent flows through the circuit, however, since the contacts 99 and 99are separated from their reeds 94 and 89 respectively. Current is alsosupplied from the lead 25 through the resistance 84 to switch blade 52and thence by way of switch contact 54 to terminal is of the vibrator24. The current passes from the terminal "l8 through the coil Hi8 and byway of the lead 94, terminal 42 and lead 44 to ground. The coil I59 istherefore energized. This attracts the reed 94 until it strikes contact98 and results in both sides of the coil I99 being connected to the reed94. The coil is therefore shorted out of the circuit and no longerattracts the reed 94.

The reed because of its spring action therefore swings in the oppositedirection and although soon thereafter the contact 98 is separated fromthe reed. 94 so as to re-energize the coil I the reed overshoots thecentral position and strikes contact 95. The circuit through thetransformer primary I 8 is therefore momentarily completed since thelead 34 is connected by way of terminal 36 and thence by lead 38 toterminal 49, the latter terminal in turn being connected through contact96 and reed 94 to ground by way of the lead 44. Soon thereafter the reed94 springs away from the contact 96, thereby opening the circuit of thetransformer primary [8 so as to repeat the cycle. During the time thereed 94 and contact 98 short out the coil I09, the resistor 84 which isconnected between the main line 25 and the movable contact 54 of thestepping relay switch protects the circuit against high current flow.

Inasmuch as the stepping relay switch contact 56 is not connected to theswinging member 52 thereof, the vibrator 22 does not operate since thecoil thereof is not energized. Under these conditions the reed 86maintains a central position between the contacts 90 and 92 such that nocircuit is made from the battery through the transformer primary [8 toground by Way of the vibrator 22. This latter vibrator therefore simplyremains in reserve until needed. At any time by depressing either thepush button 62 or the button 55 the stepping relay coil 58 can beenergized in the manner previously described so as to shift the swingingcontact 52 away from the contact 54 and against the contact 55. Thisremoves the vibrator 24 from operation and causes current to flowthrough the resistor 84 by way of stepping relay switch contacts 52 and56 to the lead 14 connected to the terminal 16. Since this latterterminal is connected to ground through the vibrator coil 88 the coil 88will attract its vibrating reed and move it against the contact 92 so asto short out the coil 88, thus permitting the reed 86 to swingbackwardly. Like the reed 94 it overshoots its central point andimpinges against the contact 90 long enough to cause a surge of cur--rent to pass from the line 25 through the transformer primary l8 andthrough contacts 90 and 86 to ground.

The periodic electrical surges in the transformer primary 18 of courseinduce like surges, excepting that they are at a stepped up voltage, inthe transformer secondary [4. These high voltage surges in a well-knownmanner cause sparking at the spark plug l so as to produce ignition forthe heater.

It will be seen that the system described provides for highvoltage'operation of the heater spark plug by a step-up transformer, theprimary of which receives low voltage current surges at high frequencyand that the transformer primary circuit is made and broken by means ofan independent vibrating switch, two of which are provided, such thateither one may be used in the circuit and that whenever one of these isused the other is disconnected from the circuit and held in reserve andfurther that the choice as to which of the vibrators is to be in thecircuit at any particular time can be determined by an operator locatedat a remote point simply by momentary actuation of an ordinary pushbutton.

Having described my invention what I claim as new and useful and desireto secure by Letters Patent of the United States is:

1. A heater ignition system of high voltage type comprising a heaterigniting spark plug, a transformer having a secondary connected forenergizing said spark plug, a primary in said transformer for energizingsaid secondary, and a circuit for energizing said primary including abattery and means connecting one side of said battery to one side ofsaid transformer primary, first and second stationary contacts arrangedin spaced apart opposed relation, a vibratable reed disposed betweensaid spaced apart contacts, electromagnetic means for attracting saidreed to said second stationary contact when energized, said reed havingsufiicient resiliency to spring from said second contact to said firstcontact when said electromagnetic means is de-energized; meansduplicating said first and second contacts, said reed and saidelectromagnetic means; circuit means connecting the other side of saidprimary to both said first contacts, circuit means connecting one sideof each of said electromagnetic means to both of said reeds and to theother side of said battery, means connecting the other side of each ofsaid electromagnetic means to its co-operating said second contact,circuit means connected to said one side of said battery and including acurrent limiting resistor, switching means for connecting the last saidcircuit alternately to either one or the other of said second contacts,electromagnetic means for operating said switching means, and remotelyoperated circuit means for operating the last said electromagneticmeans.

2. An ignition system for a heater to provide an uninterruptedsuccession of fuel igniting sparks, comprising a transformer having ahigh voltage secondary and a low voltage primary; a heater ignitingspark plug connected with the secondary for energization; a firstvibrator having first and second stationary contacts, a vibratable reedcarrying a third contact positioned between the stationary contacts, andan electromagnet adjacent the reed for pulling it toward the secondcontact for vibrating the reed, the electromagnet being shunted acrossthe second contact and the reed; a second similar vibrator; first andsecond direct current power input terminals, one side of the transformerprimary being connected with the first input terminal and the reeds ofboth vibrators being connected with the second input terminal, the otherside of the primary being connected with the first stationary contactsof both vibrators; a. current limiting resistor; a push button switch; astepping relay including a pair of contacts respectively connected withthe second contacts of the vibrators, contact means connected throughthe resistor with the first input terminal, and means including amagnetic coil for establishing a connection between the contact meansand the respective relay contacts alternately in response to successiveintervals of energization of the coil, for energizing the vibratorsalternately, one side of the coil being connected with one of the powerinput terminals, and the other side of the coil being connected throughthe push button switch with the other power input terminal.

GERALD JACOBS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,102,593 Kettering July 7, 19141,275,047 Krantz Aug. 6, 1918 1,946,607 Afiel Feb. 13, 1934 2,221,521Maycock Nov. 12, 1940 2,330,431 Klatsch Sept. 28, 1943 2,427,076Tabecchi Sept. 9, 1947

